Down draft furnace



J. E. GRENAWALT Der. 26, 1937.

Do'wN DRAFT FURNAGE Filed Aug. 19, 1935 2 Sheets-Sheet 1 J. E.GREENAWALT DowN DRAFT FURNAGE n 2 Sheets-Sheet? Filed Aug. 19,

#from/EK Patented Oct. 26, 1937 PATENT oFFlcE 2,097,153 5 DOWN DRAFTFRNAGE- John E. Greenawalt, New York, N. Y. Application August 19, 1933,'Serial No. 685,821

6 Claims.

My invention has relation to improvements in furnaces more particularlyfor down draft combustion and it consists in the novel features ofconstruction more fully set forth in the specifi- 5 cation and pointedout in the claims.

The principal object of the invention is to provide a furnace that isespecially adapted for furnishing the heat necessary to the operation ofother apparatuses, such as hot water or steam boilers,

furnaces including sintering apparatus.

incinerating furnaces and metallurgical The furnace is, therefore,essentially a primary cornbustion furnace from which the hot gases andproducts of combustion discharge to some other apparatus where the heatof the primary furnace is utilized. However, I do not wish to beunderstood as restricting the invention to association with some otherapparatus as the furnace isa completely operative device in itself.

A further object of my invention is to provide a furnace in which thefuel and the air are subjected to a swirling movement through thecombustion chamber of the furnace to insure a thorough commingling ofthe fuel and the air, thusV insuring complete combustion.

In addition to the above objects I have provided a furnace in which thefuel and air are subjected to great turbulence to eect an eX- tremelyrapid and intense combustion within the combustion chamber resulting inan extreme-V ly high temperature therein.

gitudinal section taken on a medial plane through the furnace and burnerassembly, parts of the latter being broken away and parts left inelevation; and Fig. 4 is an inside plan view of one of the fueldistributing head members showing the fuel discharge passageways.

Referring to the drawings, it will be seen that the furnace comprises acircular wall I and bottom 2 together with the removable top wall 3enclose a combustion chamber 4, in the center of which of a suitablerefractory material which is a refractory column 5 built up from thebottom 2.

The column 5 being cylindrical gives to the combustion chamber 4 anannular form and said column terminates a short distance below the lowersurface 6 of the top 3 which forms the upper bounding surface ofthe-combustion chamber so as to provide a space 'I to receive 5 a fueldistributing head 8 to be described more in detail hereinafter. Theperipheral portion l of' this space'l obviously serves as an inlet forthe fuel which will also be more fully described. An outletv 9' for theproducts of combustion is 10 formed Vinr the wall I and through anextensionV I'thereof,- said outlet leading from the bottom ofthecombustion chamber 4 Vso that the outlet will be spaced some littledistance vertically from the inlet-l". The wall I and Ibottom 2 ofthe'15 furnace are enclosed in a sheet metal casing' Ill and anangleiron flange II secured to the cas-r ing III contiguous tothe top surfaceI2 of the wallf Lon.` which the furnace top or cover 3 rests; Y Thecover 3 is formed of a circular channel- 20 shaped shell Il3having aperipheral flange I4 and suitable refractory material I5 disposed withinthe shell lf3. The inner circular wall 'I3' of the shell I3 defines anopening orY throat I6 for receiving what I choose to term a burner Bwhich furnishes the fuel to the furnace. The particular burnerillustrated is not indispensable to my improved furnace as any means forinjecting fuel and air into the furnace in proper condition for thecombustion may be utilized. However, in order that lthe invention may beclearly understood I Will describe briefly the burner B whichisillustrated.

The burner B includes the fuel distributing head above alluded to whichis rotatably mounted within theI bearing member Il supported by acylindrical housing I 8, the latter in turn being supported by thestructural members I9, I9, which also carry the furnace. 'Ihe fueldistributingv head 8 comprises a tube 20 having aconical inner surface2I widening toward the bottom of the` tube which terminates in a'flange22,'on the upper surface of which are a number of radially disposed ribsor vanes 22. A disk 23 havin-g aV central conical boss 24 and a seriesof peripheral radially disposed bosses 25 is bolted against-the-'ange 22so that the boss 24 projects Y toward: the center of the tube'20 andthebosses 25 maintaifnlthedisk in spaced relation with the fla-nge22.-1'The radially disposed bosses 25 divide `50z radiatea plurality ofyvanes 28- which operate V55 Y as fan blades on the distributing head 8,as will be apparent in the description of the operation of the furnace.A fuel pipe 29 leading from any suitable source of fluent fuel (such asoil) extends through the open end of the tube 2U so that fuel will dropin a regulated amount into said tube.

An air inlet pipe 30 controlled by a valve 3| leads into the side of thehousing I8, and a second air inlet pipe 32 controlled by a valve 33leads into an air port 34 passing through the center of the column 5.Thus, by regulating the valves 3| 'and 33 air in measured quantitieswill be conducted to both sides of the fuel distributing head 8. Asexplained above, the fuel distributing head is rotatably supported bythe bearing member l'l and is adapted toibe rapidly rotated by means ofa motor M, to which the head is directly connected by means of a shaft35 keyed to a spider 36 within the tube 2U. 31 is an oil cup from whichoil is fed through the pipe 38 to the bearings 39 `within the bearingmember Il.

The action of my improved furnace is as follows:

The oil is delivered against the inside surface of tub-e 20 from thefeed pipe 29 where it is spun out to a very thin film uniformly over theinside surface of the tube by the centrifugal force and surface tension,it being understood that the tube 2li is rotated at a very high rate ofspeed (approximately 3500 R. P. M.). On account of the conical shape ofthe tube, it being wider at the bottom than at the top, the oil lm movesslowly and evenly downwardly, all the while being whirled around theinner surface of the tube by the centrifugal force. Ultimately the oilreaches the flange 22 and as it moves outwardly over the inner surfaceof this flange it is still further attenuated on account of the increasein diameter as the oil approaches the periphery of the flange, When theoil reaches the bosses 25 between flange 22 and lower disk 23 itentersthe radial fuel passages 26, all of said passages receivingapproximately the same amount of oil on account of the uniformdistribution of the oil by the centrifugal` force over the inner surfaceof the flange 22. By the time the oil passes through the passages 26 andis about to be discharged therefrom it is not only uniformly distributedaround the fuel distributing head 8, but is also in a very ne state ofdivision, or atomization, so that it may be very easily and quicklyvaporized the instant it enters the combustion chamber 4. OfY course,air is sucked into the tube 20 through the open top thereof and this airis thoroughly mixed with the particles of oil discharging from thepassages 26. Air also passes through the housing I8 and through the port34 to both sides of the fuel distributing head 8 and enters the inlet'I' to the combustion chamber 4 on both sides of the circular spray ofmixed fuel and air issuing from the distributing head 8. There are thustwo air supplies for the fuel, the primary air supply entering thecombustion chamber 4 intimately mixed with the fuelfrom the distributinghead 8, and the secondary air supply entering the combustion chamberonboth sides of the spray of mixed fuel and air. I have found inpractice that the amount of primary air should'be between 20% and 50% ofthe entire air supply required for complete combustion, the amount ofsecondary air, of course, not being Aso critical provided there issufficient secondary air to complete the combustion of the fuel. Thevelocity with which the secondary air passes through the air and fuelintake 'l' is increased by the vanes 22' on the flange 22 and vanes 28on the disk 23. Of course, the same result may be obtained by increasingthe pressure at the source of supply of the secondary air.

The high rotative speed of the distributing head 8 causes an intenseturbulence in the circular space 'I' which serves as the fuel and airinlet. 'Ihis turbulence makes the vaporization of the fuel very rapid sothat there is obtained an explosive mixture almost as soon as the fueland the air enter the combustion chamber 4. Therefore, combustionproceeds immediately and continuously as the mixed gases are whirleddownwardly through the annular combustion chamber on their way to theoutlet 9. The locating of the outlet 9 or flue in a horizontal planebelow the inlet 'l' compels the gases and flaming particles to movedownwardly and results in high efficiency and complete combustionwithout the use of excess air and without the formation of smoke. Thecentral refractory column assists in producing this result as it givesto the combustion chamber its annular shape which cooperates with therapidly rotating distributing head to produce the swirling turbulencefor intensifying combustion.

Having described my invention, I claim:

1. A furnace for burning fluent fuel comprising side walls and top andbottom walls enclosing a combustion chamber, a fuel distributing headhaving peripheral outlets adjacent to the top wall of said chamber,means for feeding fuel to said distributing head, means for admittingair to said head, means for rotating said distributing head to projectsaid fuel and air into said combustion chamber at a velocity sufficientto prevent combustion in sai-d distributing head, means within theVVcombustion chamber for shielding the fuel distributing head from theheat of combustion, and an outlet flue for the products of combustionnear the bottom wall of said combustion chamber.

2. A furnace for burning fluent fuel comprising side walls and top andbottom walls enclosing a combustion chamber, a column disposed on thebottom wall Awithin said chamber and spaced from the side walls thereof,the top of said column also being spaced from the top wall of thecombustion chamber, means in the space between the top of said columnand'the top wall of the combustion chamber for feeding fuel and air tothe combustion chamber, and said chamber having an outlet for theproducts of combustion, said outlet being disposed near the bottom wallof the combustion chamber whereby the products of combustion are forcedto travel through the combustion chamber.

3. A furnace for burning fluent fuel comprising side walls and top andbottom walls enclosing a combustion chamber, a column disposed on thebottom wall within said chamber and spaced from the side walls thereof,said column also having one end spaced from the top wall of thecombustion chamber, means located in a plane between savid top wall andthe top of the column for discharging fuel and air into the combustionchamber, said column having a passageway for air leading to saidcombustion chamber, and said chamber having an outlet for the productsof combustion, said outlet being disposed adjacent to the bottom wall ofthe furnace.

n 4. A furnace for burning fluent fuel comprising side walls and top andbottom Walls enclosing a combustion chamber, a column disposed withinsaid chamber, the top of said column'being spaced from the top wall ofthe combustion chamber, means adjacent to said top Wall for feeding fueland primary air into the combustion chamber, said column having apassage Way for supplying secondary air to the combustion chamber, andsaid combustion chamber having an outlet for the products of combustionadjacent the bottom Wall thereof.

5. A furnace for burning liquid fuel comprising an annular combustionchamber, a circular fuel distributing head at one end of said combustionchamber, said head having peripheral discharge orifices, means forconducting air to the periphery of said head at one side thereof, meansfor rotating said head to eiect a distribution of fuel in the form of a,circular sheet, andsaid chamber having an outlet for the products ofcombustion at the end thereof opposite to the fuel distributing head.

6. A furnace for burning liquidy fuel comprising an annular combustionchamber, a fuely distributing head at one end of said combustionchamber, means for rotating said fuel distributing head to effect adischarge of fuel into the combustio-n chamber by centrifugal action,said head having its rotation axis coincident With the longitudinal axisof the combustion chamber,`

means for conducting air to the periphery of said head at both sidesthereof, and said chamber having an outlet for the products ofcombustion at the end thereof opposite to the fuel distributing head.

JOHN E. GREENAWALT.

